Electronic ignition system with pickup utilizing alternating flux to produce timed pulses of opposite phase



Oct. 12, 1965 c. L. SHANO 3,211,954

ELECTRONIC IGNITION SYSTEM WITH PICKUP UTILIZING ALTERNATING FLUX TOPRODUCE TIMED PULSES OF OPPOSITE PHASE Filed Dec. 20, 1962 5| FIG; 1a 1I I I I I I T FIG 1 OISTR/BUTOR FIG. 4

\f Char/es L. Shana f\ BY Q MXM A/Tys.

L A INVENTOR.

United States Patent 3,211,954 ELECTRONIC IGNITION SYSTEM WETH PICKUPUTILIZING ALTERNATING FLUX TU PRODEMZE TIMED PULSES 0F 0PPOKTE PHASECharles L. Shano, Morton Grove, lIll., assignor to Motorola, Inc,Chicago, Ill., a corporation of Illinois Filed Dec. 20, 1962, Ser. No.246,172 11 Claims. (Cl. 3l5-2l8) This invention relates to ignitionsystems for internal combustion engines, and more particularly to animproved transistorized ignition system utilizing a magnetic pulsingunit.

Transistorized ignition systems utilizing magnetic pulsing uni-ts offerimportant advantages over the more conventional type systems whichutilize breaker points and condensers. Nevertheless, numerous problemsarise in connection with the transistorized systems. For example, at lowcranking speeds the triggering pulses generated by the magnetic uni-tsare very weak and hence unsure in their triggering effect. Anotherdifficulty with electronic systems is that transient signals may causefalse triggering of the ignition system. Finally, at high speeds thevoltage pulses generated in the ignition system may be suflicient todamage the transistor switching devices.

Accordingly an object of this invention is to provide a transistorizedignition system which produces good pulse voltage values at low crankingspeeds.

Another object of the invention is to provide a reliable, suretriggering transistorized ignition system utilizing a pulse producingmechanism of rugged construction.

Another object of the invention is to provide a transistorized ignitionsystem which reduces the danger of transient signals triggering theignition circuit.

Another object of the invention is to provide means in a transistorizedignition system for preventing damage to the switching transistors athigh operating speeds.

A feature of the invention is the provision in a transistorized ignitionsystem, of a magnetic pulser producing pulses of alternate polarity Witha transistorized switching circuit and a dual coil pickup, and ofcircuitry connecting the switching circuit to the pickup to trigger thetransist-orized system on each of the alternate pulses.

Another feature of the invention is a megnetic pulser unit having a diskmagnet sandwiched between a pair of pole plates, each of the pole plateshaving extensions with oblique pole faces thereon. A pickup member hassimilar pole faces so that magnetic flux theretrhrough is suddenlyweakened at timed intervals, with alternate pairs of the extensionscausing alternating flux directions through the pickup member.

Another feature of the invention is the provision, in an ignition systemutilizing the above described magnetic pulser, of a single transistorand a pair of diodes for steering the pulses to cause the desiredswitching of the transistor.

A further feature of the invention is the provision, in such an ignitionsystem, of a pair of switching transistors operating in alternatingfashion to present triggering pulses to the high voltage output.

Still another feature of the invention is the provision, in thedescribed ignition system, of protective means connected to the coilwindings to shunt excessive voltages from the transistor switchingcircuits. The protective means may be in the form of varistors, Zenerdiodes or low pass filters for shunting high frequency high voltagepulses from the transistor switching circuits.

A still further feature of the invention is the provision of a buckingwinding opposing the voltage induced in the coil of the pulser unit toreduce excessively high voltages therein and prevent damage to thetransistors.

In the drawings:

FIG. 1, is a schematic diagram of the ignition system constructed inaccordance with the invention;

FIG. 1a, is a side elevational view of the rotor of the pulsing unit ofFIG. 1;

FIG. 2, is an enlarged broken away View depicting in phantom the motionof the pulse generator of FIGS. 1 and la,

FIG. 3 depicts the changes in flux and voltage in the pickup member ofFIG. 1;

FIG. 4, is a schematic diagram of a second. embodiment of the invention;and

FIG. 5, is a schematic diagram of still another embodiment of theinvention.

In practicing the invention, a pulsing unit is provided with a magneticrotor assembly. This rotor assembly includes a permanent disc magnetsandwiched between two annular pole plates. The pole plates haveinterleaved projections extending outwardly therefrom so that as theassembly rotate-s, alternate north and south pole .pieces are presentedto two aligned pole extensions of a pickup which completes a magneticcircuit between the alternating pole pieces. As the pole pieces pass bythe aligned extensions of the pickup member, the oblique faces on theextensions of the pickup member and the projections: of the pole piecespresent a gradually diminishing and then rapidly increasing air gaptherebetween.

A center tapped coil on the pickup member has alternating voltagesinduced therein due to the changing directions of the flux through thepickup member. These pulses are used to trigger a first circuit which inturn triggers the high voltage output circuit supplying high voltageignition pulses to the internal combustion engine. One version of thefirst circuits includes a pair of steering diodes and a single switchingtransistor, while another version includes a pair of transistorsalternately switching on and olf. Protection from high voltage damage isafforded to the transistors in various ways, including a pair ofvaristors connected across the coils, a low pass filter network, and apair of zener diodes connected across the coils, or by the use of abucking Winding opposing the voltage induced in the coils.

Referring to FIG. 1, pulses for switching an ignition system for aninternal combustion engine 11 are supplied by a magnetic pulsing unitwhich includes a pickup member 13 and a center tapped coil includingwindings 15 and 17. Flux is varied through the magnetic pickup member 13by a rotor assembly 19. Referring also now to FIG. 1a, the constructionof rotor assembly 19 may be seen. A disk shaped permanent magnet 21 issandwiched between two annular pole plates 23 and 25 and the assemblymay be driven in sychronism with internal combustion engine 11 on rotarydrive shaft 27. With the polarity of magnet 21 as shown in FIG. la, poleplate 23 will provide north poles and plate 25 will provide south oles.p The pole plates 23 and 25 are provided with a plurality of projections29. The number of projections 29 will be determined by the number ofcylinders of the internal combustion engine 111. As will be apparentfrom the drawings, the projections 25' of the pole plates 23 and 25 areinterleaved, and will alternately appear as rotor assembly 19 rotates inthe direction of the arrow. Thus each time a pair of projections 29align themselves with the extensions of pickup member 13, a flux pathwill be completed through member 13. The direction of this flux pathwill change as each succeeding pair of projections 29 are alignedtherewith.

It will also be apparent that projections 29 are obliquely angled ontheir ends, as are the corresponding extensions of pickup 13. Because ofthis, as the projections 29 swing past the extensions of pickup member13 the gap therebetween will gradually close and then open verysuddenly. This is more clearly shown in FIG. 2. A rapid change of fluxthrough member 13 occurs when the air gap is suddenly increased. Theseflux values are depicted in the top curve of FIG. 3, and the point wherethe rapid change occurs may be readily seen. Such a change in fluxgenerates peak voltages of opposite polarities in windings 15 and 17, asshown in the lower curve of FIG. 3.

A pair of diodes 31 and 33 connect the ends of Windings 15 and 17 to thebase 35 of a transistor 37. The other ends of windings 15 and 17 areconnected through a common lead 39 to the emitter 41 of transistor 37.Windings 15 and 17 have voltages generated therein 180 out of phase witheach other as indicated by the dots. When the voltage generated inwindings 17 is in the direction to cause transistor 37 to conduct, thevoltage generated in winding 15 is in the direction to reverse biasdiode 33. The following pulse will reverse bias diode 31 and willconduct through diode 33. As a result, every pulse which appears inwindings 15 and 17 will cause transistor 37 to conduct.

The emitter electrode 41 of transistor 37 is connected to a positivevoltage source 43. The collector electrode 45 of transistor'37 isconnected to the primary winding 47 of a high voltage transformer 49.Accordingly when transistor 37 is conductive, primary winding 47 oftransformer 49 will be energized to induce a voltage in secondarywinding 51. Secondary winding 51 of transformer 25 is connected acrossbias electrodes 53 and emitter electrodes 55 of output transistor 57.Thus when the voltage is induced in secondary winding 51, outputtransistor 57 will be turned on. Transistor 57 is connected to theprimary winding 59 of a high voltage transformer 61 for energizing thesame. Thus when transistor 57 is energized, high voltage will besupplied to transformer 61. The secondary winding 63 of transformer 61is connected to distributor 13. Upon collapse of the field of highvoltage transformer 61, the high voltage spike resulting therefrom issupplied to distributor 13 and hence to internal combustion engine 11for igniting the fuel therein.

When transistor 37 conducts, current amplification occurs which causesoutput transistor 57 to conduct and saturate due to phase relationshipin transformer 49. As the pulse disappears, transistor 57 suddenlychanges from saturation to cutoff. This rapid change of current throughprimary winding 59 of transformer 61 creates the required flux linkagesto cause the necessary high voltage to appear in the secondary winding63 of transistor 61. The energy to arc across the sparkplug gap in thesparkplug of internal combustion engine 11 is thereby attained. Acapacitor 67 connects the collector 69 of transistor 57 to the base 35of transistor 37 in regenerative fashion such that it aids in speedingup the rate of current rise and decay in the primary 59 of transformer61.

No temperature compensation is required in the circuit since the inputpulse under all conditions of temperature and cranking speed will beadequate to cause transistor 37 to saturate. Because no forward bias isused on either of transistors 37 or 57, the circuit will not besensitive to random line voltage changes.

During high speed operation, rapidly changing flux in pickup 13 mayinduce very high voltages in coils 15 and 17. Damage to transistor 37may be prevented by connecting a pair of varistors 71 and 73 acrosscoils 15 and 17 respectively. The varistors have the characteristic thattheir resistance is inversely proportional to the voltage appliedthereto. Thus at low generator voltage, the resistance will be high withnegligible effect on the system. At high voltages, however, theresistances will be low providing a heavy shunt on the coils at highspeeds.

Referring now to FIG. 4, a further embodiment of the invention is shown.A pair of transistors 75 and 77 have their emitter electrodes 79 and 31respectively connected to common lead 39. The collector electrodes 83and 85 of transistors 75 and 77 respectively are connected to either endof the primary winding 47 of transformer 49.

Primary winding 47 has a grounded center tap 87. Regenerative feedbackcapacitors 89 and 91 are connected to the base electrodes 93 and 95 oftransistors 75 and 77 respectively in the same manner as capacitor 67 inFIG. 1.

The embodiment shown in FIG. 4 should result in improved stability. Whenthe pulse in coil 17 causes transistor 75 to conduct, the pulse in coil15 will cause transistor 77 to be cut off. The following pulse causesthe opposite effect. The two halves of primary winding 47' are connectedto their respective collectors 83 and such that when either transistor75 or transistor 77 is on, the secondary winding 51 of transformer 49will cause transistor 57 to conduct in the manner previously described.

Varistors 71 and 73 of FIG. 1 could be used in a similar manner in thepresent embodiment.

Another way of limiting the voltage in either of these two embodimentswould be the connection of a low pass filter network in the base circuitfor each transistor. This is shown by resistor 97 and capacitor 99 inthe circuit for base 93 of transistor 75, and by resistor 101 andcapacitor 103 in the circuit for base of transistor 77. As the speed ofrotation of rotor assembly 19 increases with the speed of internalcombustion engine 11, and hence as the voltages generated in coils 15and 17 increase, the frequency will increase accordingly. Thus,increasing amounts of the voltage will be shunted from the bases of therespective transistors. For improved filtering, resistors 97 and 101could be replaced by inductors.

Another method of limiting the voltage generated in coils 43 and 45 isshown in FIG. 5. Here a flux bucking coil 105, which may be wound on thepickup member 13, is provided to oppose the current generated in coils15 and 17. Thus as the voltage generated increases, the current in theflux bucking coil 105 is directed to set up a field opposing the flux incoils 43 and 45, causing a re duction in the voltage generated therein.A variable resistor 107 and a diode 109 complete the flux bucking coilcircuit. Diode 109 in series with bucking coil 107 prevents current flowin the "bucking coil until the voltage across the bucking coil is largeenough to overcome the forward bias of diode 109. Resistor 107 isadjusted to provide the correct current magnitude for control of thevoltage applied to the bases of transistors 75 and 77.

FIG. 5 shows a further voltage safety device for the transistors. Thisinvolves the connection of a pair of zener diodes 111 and 113 acrosscoils 43 and 45 respectively. Output voltages of the coils exceeding thezener breakdown value will cause the diodes to shunt current from thebases of the respective transistors to prevent damage thereto. The fluxbucking winding and the zener diodes may each be used without the otherto provide some protection against high generated voltages, as may berequired.

It may therefore be seen that the invention provides an improvedignition system for an internal combustion engine, which system isreliable and of rugged construction. Good pulse values are obtained atall speeds of the engine, and features are included to prevent overloadon the switching transistors at high operational speeds. Finally,transient signals and variations in the power supply will not affect theoperation of the system.

I claim:

1. An ignition system for an internal combustion engine, including incombination, high voltage output means supplying high voltage ignitionpulses to the internal combustion engine, transistor switching meanscontrolling said high voltage output means, magnetic pulser meansoperable in synchronism with the internal combustion engine and having amagnetic structure including a pick up member wherein the direction ofmagnetic flux is alternately reversed in the operation of said pulsermeans, a pair of windings on said pickup member to produce alternatingpulse voltage waves of opposite phase for controlling said transistorswitching means, and circuit means connecting said windings to saidtransistor switching means for controlling same, said circuit meansincluding first and second portions individually connected to saidwindings and each applying alternate half cycles of the voltage pulsewaves induced in one of said windings to control operation of saidtransistor switching means, whereby said high voltage output means issupplied with control pulses for each of the alternate flux directionsproduced by said magnetic pulser means.

2. An ignition system for an internal combustion engine, including incombination, high voltage output means supplying high voltage ignitionimpulses to the internal combustion engine, transistor switching meanscontrolling said :high voltage output means, magnetic pulser meansoperable in synchronism with the internal combustion engine and having amagnetic structure including a pickup member in which magnetic flux isalternately produced in opposite directions by the operation of saidmagnetic pulser means, a pair of windings on said pickup member in whichalternating voltage pulses are induced for controlling said transistorswitching means, and circuit means connecting said windings to saidtransistor switching means for controlling the same, said circuit meansincluding first and second portions individually connected to saidwindings and each alternately applying the portion of the alternatingvoltage pulses of one polarity induced in one of said windings to switchon said transistor switching means, whereby said high voltage outputmeans is supplied'with control pulses for each of the alternate fluxdirections produced by said magnetic pulser means.

3. An ignition system for an internal combustion engine including incombination, high voltage output means supplying high voltage ignitionpulses to the internal combustion engine, a transistor switchcontrolling said high voltage output means, magnetic pulser meansoperable in synchronism with the internal combustion engine and having apickup member wherein the direction of magnetic flux is alternatelyreversed in the operation of said pulser means, a pair of windings onsaid pickup member to produce alternating pulse voltage waves ofopposite phase for controlling said transistor switch, and a pair ofdiodes each connected to one of said-windings and connected to the baseof said transistor switch for providing bias current thereto, saiddiodes being poled to block positive pulses from passage therethrough,whereby said diodes will pass alternate half cycles of the voltage pulsewaves induced in each of said windings to cause said transistor switchto conduct, whereby said high voltage output means is supplied withcontrolpulses for each of the alternate flux directions produced by saidmagnetic pulser means.

4. An ignition system 'for an internal combustion engine, including incombination, high volt-age output means supplying high voltage ignitionpulses to the internal combustion engine, a pair of transistorsconnected to provide current for controlling said high voltage outputmeans, magnetic pulser means operable in synchronism with the internalcombustion engine and having a pickup member wherein the direction ofmagnetic flux is alternately reversed in the operation of said pulsermeans, a pair of windings on said pickup member to produce alternatingpulse voltage waves of opposite phase for controlling said high voltageoutput means, and circuit means connecting each of said windings torespective ones of the base electrodes of said pair of transistors,whereby said transistors will be alternately turned on to control saidhigh voltage output means during alternate half cycles of the voltagepulse waves induced in each of said windings, whereby said high voltageoutput means is supplied with control pulses for each of the alternateflux directions produced by said magnetic pulser means.

5. An ignition system for an internal combustion engine including incombination, high voltage output means supplying high voltage ignitionpulses to the internal combustion engine, transistor switching meanscontrolling said high voltage output means, magnetic pulser meansoperable in synchronism with the internal combustion engine and having arotatable wheel therein with a plurality of oblique pole faces, saidpulser means further including a pickup member having a pair of obliquepole faces adapted to mate with successive pairs of said plurality ofoblique pole faces on said rotatable member, said pole faces operatingto present a gradually diminishing and suddenly increasing air gaptherebetween, said magnetic pulser means operating to alternatelyreverse the direction of magnetic flux through said pickup member, apair of windings on said pickup member to produce alternating pulsevoltage waves of opposite phase for controlling said transistorswitching means, and circuit means connecting said winding to saidtransistor switching means for controlling same, said circuit meansapplying alternate half cycles of the voltage pulse waves induced ineach of said windings to control operation of said transistor switchingmeans, whereby said high voltage output means is supplied with controlpulses for each of the alternate flux directions produced. by saidmagnetic pulser means.

6. An ignition system for an internal combustion engine including incombination, high voltage output means supplying high voltage ignitionpulses to the internal combustion engine, transistor switching meanscontrolling said high voltage output means, magnetic pulser meansoperable in synchronism with the internal combustion engine, saidmagnetic pulser means including a disc type magnet sandwiched betweenfirst and second plates, said first and second plates having alternateinterleaved projections thereon, each of said projection-s having anoblique pole face, said magnetic pulser means further including a pickupmember having a pair of oblique pole faces for alternately mating withsuccessive pairs of said pole faces on said projections of said firstand second plates, whereby the direction of magnetic flux in said pickupmember is alternately reversed as said pole faces on said projections ofsaid first and second plates pass by said pole faces on said pickupmember, said pole faces presenting a gradually diminishing and suddenlyopening air gap in the magnetic circuit, a pair of windings on saidpickup member to produce alternating pulse voltage waves of oppositephase for controlling said transistor switching means, and circuit meansconnecting said windings to said transistor switching means forcontrolling the same, said circuit means applying alternate half cyclesof the voltage pulse waves induced in each of said windings to controloperation of said transistor switching means, whereby said high voltageoutput means is supplied with control pulses for each of the alternateflux directions produced by said magnetic pulser means.

7. An ignition system for an internal combustion engine including incombination, high voltage output means supplying high voltage ignitionpulses to the internal combustion engine, transistor switching meanscontrolling said high voltage output means, magnetic pulser meansoperable in synchronism with the internal combustion engine and having apickup member in which magnetic fiux is alternately reversed indirection by the operation of said magnetic pulser means, a pair ofwindings on said pickup member in which alternating voltage pulses areinduced for controlling said transistor switching means, circuit meansconnecting said windings to said transistor switching means forcontrolling the same, said circuit means alternately applying theportion of the alternating voltage pulses of one polarity induced ineach of said windings to switch on said transistor switching means,whereby said high voltage output means supplied with control pulses foreach of the alternate flux directions produced by said magnetic pulsermeans, said circuit means including shunt means connected across saidwindings on said pickup member and adapted to shunt current from saidtransistor switching means when the voltage generated in said windingson said pickup member exceeds a given value.

8. An ignition system for an internal combustion engine including incombination, high voltage output means supplying high voltage ignitionpulses to the internal combustion engine, transistor switching meanscontrolling said high voltage output means, magnetic pulser meansoperable in synchronism with the internal combustion engine and having apickup member in which magnetic flux is alternately reversed indirection by the operation of said magnetic pulser means, a pair ofwindings on said pickup member in which alternatnig voltage pulses areinduced for controlling said transistor switching means, circuit meansconnecting said windings to said transistor switching means forcontrolling the same, said circuit means alternately applying theportion of the alternating voltage pulses of one polarity induced ineach of said windings to switch on said transistor switching means,whereby said high voltage output means is supplied with control pulsesfor each of the alternate flux directions produced by said magneticpulser means, said circuit means including varistor means connectedacross said windings on said pickup member for shunting current fromsaid transistor switching means when the voltage produced in saidwindings exceeds a given value.

9. An ignition system for an internal combustion engine including incombination, high voltage output means supplying high voltage ignitionpulses to the internal combustion engine, transistor switching meanscontrolling said high voltage output means, magnetic pulser meansoperable in synchronism with the internal combustion engine and having apickup member in which magnetic flux is alternately reversed indirection by the operation of said magnetic pulser means, a pair ofwindings on said pickup member in which alternating voltage pulses areinduced for controlling said transistor switching means, circuit meansconnecting said windings to said transistor switching means forcontrolling the same, said circuit means alternately applying theportion of the alternating voltage pulses of one polarity induced ineach of said windings to switch on said transistor switching means,whereby said high voltage output means is supplied with control pulsesfor each of the alternate flux directions produced by said magneticpulser means, said circuit means including means for shunting highfrequency pulses produced in said Windings on said pickup member fromsaid transistor switching means, whereby high voltages produced by highspeed operation are prevented from damaging said transistor switchingmeans.

10. An ignition system for an internal combustion engine including incombination, high voltage output means supplying high voltage ignitionpulses to the internal combustion engine, transistor switching meanscontrolling said high voltage output means, magnetic pulser meansoperable in synchronism with the internal combustion engine and having apickup member in which magnetic fiux is alternately reversed indirection by the operation of said magnetic pulse means, a pair ofwindings on said pickup member in which alternating volt-age pulses areinduced for controlling said transistor switching means, circuit meansconnecting said windings to said transistor switching means forcontrolling the same, said circuit means alternately applying theportion of the alternating voltage pulses of one polarity induced ineach of said windings to switch on said transistor switching means,whereby said high voltage output means is supplied with control pulsesfor each of the alternate flux directions produced by said magneticpulser means, said circuit means including zener diode means connectedacross said windings of said pickup member to shunt current from saidtransistor switching means when the voltage of said coils attains thezener breakdown value.

11. An ignition system for an internal combustion engine, including incombination, high voltage output means supplying high voltage ignitionpulses to the internal combustion engine, transistor switching meanscontrolling said high voltage output means, magnetic pulser meansoperable in synchronism with the internal combustion engine and having apickup member in which magnetic flux is alternately reversed indirection by the operation of said magnetic pulser means, a pair ofwindings on said pickup member in which alternating voltage pulses areinduced for controlling said transistor switching means, a buckingwinding on said pickup member, and first circuit means connected to saidbucking winding to cause same to be operable at a given value of voltageinduced in said Windings, and second circuit means connecting said pairof windings to said transistor switching means for controlling the same,said second circuit means alternately applying the portion of thealternating voltage pulses of one polarity induced in each of said pairof windings to switch on said transistor switching means, whereby saidhigh voltage output means is supplied with control pulses for each ofthe alternate flux directions produced by said magnetic pulser means.

References Cited by the Examiner UNITED STATES PATENTS DAVID J. GALVIN,Primary Examiner.

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE, INCLUDING INCOMBINATION, HIGH VOLTAGE OUTPUT MEANS SUPPLYING HIGH VOLTAGE IGNITIONPULSES TO THE INTERNAL COMBUSTION ENGINE, TRANSISTOR SWITCHING MEANSCONTROLLING SAID HIGH VOLTAGE OUTPUT MEANS, MAGNETIC PULSER MEANSOPERABLE IN SYNCHRONISM WITH THE INTERNAL COMBUSTION ENGINE AND HAVING AMAGNETIC STRUCTURE INCLUDING A PICK UP MEMBER WHEREIN THE DIRECTION OFMAGNETIC FLUX IS ALTERNATELY REVERSED IN THE OPERATION OF SAID PULSERMEANS, A PAIR OF WINDINGS ON SAID PICKUP MEMBER TO PRODUCE ALTERNATINGPULSE VOLTAGE WAVES OF OPPOSITE PHASE FOR CONTROLLING SAID TRANSISTORSWITCHING MEANS, AND CIRCUIT MEANS CONNECTING SAID WINDINGS TO SAIDTRANSISTOR SWITCHING MEANS FOR CONTROLLING SAME, SAID CIRCUIT MEANSINCLUDING FIRST AND SECOND PORTIONS INDIVIDUALLY CONNECTED TO SAIDWINDINGS AND EACH APPLYING ALTERNATE HALF CYCLES OF THE VOLTAGE PULSEWAVES INDUCED IN ONE OF SAID WINDINGS TO CONTROL OPERATION OF SAIDTRANSISTOR SWITCHING MEANS, WHEREBY SAID HIGH VOLTAGE OUTPUT MEANS INSUPPLIED WITH CONTROL PULSES FOR EACH OF THE ALTERNATE FLUX DIRECTIONSPRODUCED BY SAID MAGNETIC PULSER MEANS.